1. Field of the Invention
The present invention relates to a novel method of producing polyesters, particularly aromatic polyesters.
2. Description of the Prior Art
Among polyesters, aromatic polyesters have nowadays been used and promised as engineering plastics for many uses such as electric parts, electronic parts and automobile parts, because they have many splendid properties such as exceedingly high heat-resistant and wear-resistant properties and high glass-transition temperature. For producing such aromatic polyesters, there have been known methods such as solution polycondensation and interfacial polycondensation of diphenols and dicarboxylic acid dihalides, melt polycondensation of dicarboxylic acids and diacetates of diphenol and of diphenols and dicarboxylic acid diphenyl esters. These methods are indirect polymerization methods wherein dicarboxylic acid is first converted to dihalogenide thereof or diphenyl ester thereof which is further reacted with diphenol, or wherein diphenols are first converted to diacetate thereof which is further reacted with dicarboxylic acid, so that they have drawbacks that they are expensive in raw materials and cumbersome in process. Therefore, a method has been desired which can produce aromatic polyesters in a more simple and cheap way.